Fluid expansion bladder

ABSTRACT

An expandable bladder for permitting expansion of a fluid within the bladder due to temperature, pressure or chemical changes without damage to fragile members adjacent the fluid. The thin, flexible, fluidtight bladder is disposed about a pool of liquid having gas dissolved therein and a fragile member located adjacent thereto. When fluid expansion occurs the bladder member is displaced by the gas or liquid to provide accommodation therefor, thus preventing any substantial fluid pressure force from acting on the fragile member.

United States Patent Robert E. Plank Willow Grove, Pa. 788,556

Jan. 2, 1969 Oct. 26, 1971 General Electric Company FLUID EXPANSION BLADDER 7 Claims, 2 Drawing Figs.

References Cited UNITED STATES PATENTS Bacon lnventor Appl. No. Filed Patented Assignee 2,078,835 4/1937 Brisson Primary Examiner-Winston A. Douglas Assistant Examiner-H. A. Feeley Attorneys-William G. Becker, Paul F. Prestia, Allen E.

Amgott, Henry W. Kaufmann, Frank 1.. Neuhauser and Oscar B. Waddell ABSTRACT: An expandable bladder for permitting expansion of a fluid within the bladder due to temperature, pressure or chemical changes without damage to fragile members adjacent the fluid. The thin, flexible, fluidtight bladder is disposed about a pool of liquid having gas dissolved therein and a fragile member located adjacent thereto. When fluid expansion occurs the bladder member is displaced by the gas or liquid to provide accommodation therefor, thus preventing any substantial fluid pressure force from acting on the fragile member.

FLUID EXPANSION BLADDER BACKGROUND OF THE INVENTION The subject invention generally relates to protective and sealing members for devices containing a pool of liquid and, in particular, to means for preventing damage due to fluid expansion in such devices.

Many devices are made which include a pool of liquid having gas dissolved therein which is enclosed by fragile members. A large percentage of these devices are electrochemical in nature wherein the liquid pool is an electrolyte and the fragile member may be used as an electrode, catalyst or semipermeable membrane. The liquid pool is generally sealed within the device by a rigid enclosure. However, applications of the devices in environmental conditions such as those found under the sea or within the upper atmosphere or outer space pose special problems due to large pressure and temperature changes that may be encountered. Particularly, changes in temperature and pressure which cause gas to be released from the liquid pool or expansion of the liquid itself can produce significant stresses acting on the fragile members enclosing the liquid, possibly resulting in damage thereto. This results in making the devices unsuitable for such applications.

SUMMARY OF THE INVENTION Accordingly, it is an object of the subject invention to provide means for protecting fragile members in a device including an enclosed pool of liquid.

Another object of the subject invention is to provide means for accommodating fluid expansion in an enclosed pool of liquid while additionally providing a fluid seal.

The above-stated objects are fulfilled by providing a thin, expandable bladder as a seal about a pool of liquid having gas dissolved therein and a fragile member adjacent thereto. When gas is released from the liquid or the liquid expands, the bladder is displaced so as to relieve any fluid pressure acting on the other members enclosing the pool of liquid.

The subject matter which is regarded as the present invention is particularly pointed out and distinctly claimed in the concluding portion of the specification.

BRIEF DESCRIPTION OF THE DRAWING The present invention, however, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing in which:

FIG. 1 is a side sectional view of a sensor utilizing the subject invention;.and

FIG. 2 is a side sectional view of a two-layer bladder in accordance with the subject invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. I there is shown an oxygen sensor in cross-sectional view, including the preferred embodiment of the subject invention.

Enclosing the sensor is a circularly cylindrical housing 1. The larger diameter end of said housing 1 has threadedly fastened therein an annular, metal retainer 2.

A plastic-insulating insert 3 closes the lower open end of housing 1. Insert 3 is comprised of essentially two bosses joined by a common washer leg portion which is rested against an expandable bladder 4, which will be described in further detail below. The larger boss of insert 3 is threaded so that it may be retained firmly by a washer 5 and a nut 6. A threaded filler hole in the center of insert 3, in which a plastic screw 7 has been inserted, facilitates filling of a liquid electrolyte 8 into the body of the sensor to form a liquid pool. The smaller diameter boss insert extends within a cylindrical porous anode 9 which may be made of any suitable material such as copper, cadmium or silver.

A porous disc cathode 12 having on its upper side a layer of gold or platinum metal is provided above the liquid pool to act as a combination catalyst and electrode. Porous disc 12 is formed of sintered metallic material which is quite brittle. A fluidtight seal is effected about porous disc I2 by the upper portion of bladder 4 which is pressed against the upper surface of disc 12 by a washer 13 which is forced against the bladder by retainer 2.

Insulated conductors 10 and II which are sealed within passageways located within insert 3 are respectively con nected to anode 9 and cathode 12 at one end. Connecting the other ends of conductors II and 12 is a load represented as a resistor 14, which may, depending upon the use of a sensor, be a meter winding or the winding of a calibrated relay or similar instrument A nylon felt washer 15 which is saturated with electrolyte 8, serves to electrically insulate cathode 12 from anode 9.

A plastic, gas permeable barrier 16, of the same diameter as catalytic cathode 12 is placed between it and washer I3 to control the rate of influx oxygen to the cathode.

In operation, oxygen diffusing through barrier I6 passes through cathode 12 where it combines with the water of electrolyte 8, acquiring electrons from cathode I2, and forming hydroxyl ions. The material of the anode 9 (for example, copper) loses electrons which flow through conductor 10, load 14, conductor 11 to cathode 12. The copper combines with hydroxyl ions from electrolyte 8 fonning cupric oxide and water. Since all of these reactions proceed stoichiometrically in accordance with Faraday's laws of electrolysis, the current through load 14 is a measure of the rate of arrival of oxygen at the face of electrode 12, and consequently the partial pressure of oxygen at the exposed side of barrier 16.

The use of expandable bladder 4, which is substantially cylindrical in shape, surrounding the pool of electrolyte prevents damage to fragile members such as sintered disc 12 and porous copper anode 9 due to release of gas from the liquid or expansion of the liquid. When expansion of the liquid or release of gases from the liquid occurs, the expandable bladder 4 is displaced radially outward due to the fluid pressure exerted by the liquid or gases. Any fluid trapped between the outer surface of the bladder 4 and the inner surface of the housing 1 is released through vent holes 17 in the housing when the bladder is displaced radially outward. The upper and lower ends of bladder 4 are clamped between members of the sensor so as to provide a seal for the fluid therein.

For proper operation, bladder 4 must be sufficiently expandable so that it may be easily displaced to quickly accommodate fluid expansion and thereby prevent fluid pressures from damaging fragile members in contact with the fluid. It is preferable, but not necessary for the bladder to be resilient so that it may stretch to accommodate the expanded fluid. For example, the expandable bladder may include a corrugated portion which is displaced to accommodate the fluid expansion without relying on the resiliency of the bladder material. Of course, the corrugations must be sufficiently flexible to allow displacement of the corrugated portion. Also, the bladder should be of a material which is unaffected by the fluids within the device and which will prevent contaminants, either solid or fluid, from passing through the bladder into the pool of liquid. Accordingly, the bladder may be of a single layer, multilayer, or coated construction, in its preferred form including plastics or synthetic or natural rubbers. The bladder shown in FIG. 1 is of a single layer of neoprene construction. FIG. 2 shows a two-layer construction with neoprene on the inside and butyl rubber on the outside; the neoprene being impervious to the electrolyte 8 within the sensor and the butyl rubber prohibiting oxygen from going through the bladder into the electrolyte 8.

The subject invention may be used in many other devices such as hydrogen sensors, fuel cells, and batteries, wherever a fragile member is located adjacent a pool of liquid wherein the device may be subjected to large pressure and temperature variations. Examples of some of the more fragile members which should be protected are highly porous, brittle members, thin membranes which have been stretched tightly, and very thin diaphragm members such as thin, steel or aluminum diaphragms.

The protective means of the subject invention is generally not needed under normal environmental conditions. However, it is a necessity where a device is to be subjected to a wide range of temperature or pressure conditions. Therefore, the subject invention is particularly useful in applications where the environment is within water, the upper atmosphere, outer space, environmental chambers where the pressure or temperature is substantially different from normal atmospheric conditions and in certain places on the earth's surface where temperature or pressure extremes prevail, such as in tropical areas, the arctic and antarctic regions and high altitudes.

Thus, the subject invention provides inexpensive and simple means for protecting fragile members from fluid pressure forces which can be installed in a device with little, if any, modification which can additionally serve as a fluid seal.

What I desire to secure by Letters Patent of the United States is 1. In an electrochemical device comprised of a casing and within the casing a pool of electrolyte, a porous consumable anode with its inner surface in contact with said pool of electrolyte, and a gas permeable, fragile cathode spaced from said anode by a separatorcontaining an electrolyte, forming a portion of a complete enclosure around said pool of electrolyte and in contact with said electrolyte, the improvement comprising:

an expandable bladder disposed about the outer surface of said anode and within said casing and adapted to form a portion of a complete enclosure around said pool of electrolyte so as to help seal said electrolyte within said device and accommodate increases in internal fluid pressure due to gases released from said pool of electrolyte and thermal expansion of said electrolyte.

2. A device as in claim 1 wherein said bladder is resilient.

3. A device as in claim 1 wherein said bladder is substantially cylindrical in shape and is expandable in a radial direction.

4. A device as in claim 1 wherein said bladder is impervious to said liquid in said device and is substantially gastight.

5. A device as in claim 3 wherein said bladder is at least partially formed of neoprene.

6. A device as in claim 1 wherein said bladder is of a multilayer construction.

7. A device as in claim 6 wherein said bladder includes a layer of neoprene and a layer of butyl rubber.

l i i It 

2. A device as in claim 1 wherein said bladder is resilient.
 3. A device as in claim 1 wherein said bladder is substantially cylindrical in shape and is expandable in a radial direction.
 4. A device as in claim 1 wherein said bladder is impervious to said liquid in said device and is substantially gastight.
 5. A device as in claim 3 wherein said bladder is at least partially formed of neoprene.
 6. A device as in claim 1 wherein said bladder is of a multilayer construction.
 7. A device as in claim 6 wherein said bladder includes a layer of neoprene and a layer of butyl rubber. 